Continuous internal stiff-gel mixer



Nov. 3, 1964 E. H. AHLEFELp, JR., ETAL CONTINUOUS INTERNAL STIFF-GELMIXER` Filed May 15, 1962 8 Sheets-Sheet l D.. l S. J, w, l. u f m $5 rMJQAS A H. H Y wmf 0 @W/ Y B 8 Sheets-Sheet 2 E. H. AHLEFELD, JR., ETALCONTINUOUS INTERNAL STIFF-GEL MIXER H c A .m .F..Ll l 1111111111: Wr m.Q s@ J ,D .:ls, vl M .7 om, l i @i @11. n m@ v lll .MTP q Nov. 3, 1964Filed May 15, 1962 Nov. 3, 1964 E. H. AHLEFELD, JR., ETAL 3,154,808

CONTINUOUS INTERNAL STIFF-GEL MIXER 8 Sheets-Sheet 3 Filed Hay 15, 19628 Sheets-Sheet 4 E. H. AHLEFELD, JR., ETAL CONTINUOUS INTERNAL STIFF-GELMIXER Nov. 3, 1964 Filed May 15, 1962 \\7// n, .m .f P

Nov. 3, 1964 E. H. AHLEFELD, JR., ETAL 3,154,803

CONTINUOUS INTERNAL STIFF-GEL MIXER Filed May 15, 1962 8 Sheets-Sheet 5Nov. 3, 1964 E. H. AHLEFELD, JR., ETAL 3,154,303

CONTINUOUS INTERNAL snFF-GEL MIXER Filed May 15, 1962 8 Sheets-Sheet 6Nov. 3, 1964 E. H. AHLEFELD, JR., EI'AL CONTINUOUS INTERNAL STIF'F-GELMII'LR 8 Sheets-Sheet 7 Filed lay 15, 1962 S m@ w mw; mf M.. mm2@ AMins. m www ma@ Nov. 3, 1964 E. H. AHLEFELD, JR., ETAL CONTINUOUSINTERNAL STIFF-GEL MIXER Filed May 15, 1962 8 Sheets-Sheet 8 UnitedStates Patent O CONTINUGUS ENTE? All STLTEGEL MT Edwin H. Ahieield,ltr., and Arnold 3. Baldwin, Woodbridge, Peter Hold, Miiforf, Walter A..Rapetshi,

Orange, and Hans R. Scharer, Wailingiord, Conn.,

assignors to Farrel Corporation, a corporation of Connecticut Filed Mayl5, 1962, Ser. N lil/,814 11 Claims. (Cl. 18-2) This invention relatesto a continuous internal mixer capable of mixinU not only sti-gels ingeneral but also the rubbers, elastomers, and plastics which heretoforecould be handled only by batch-type machines. For example, heretoforethe dispersion of carbon black in rubber and the plasticizing ofunplasticized polyvinyl chloride and rigid polyvinyl chloride undercommercial working conditions, have necessitated the use of either anopen roll mill or an internal mixer. These can handle material only inbatches.

Some prior art U.S. patents indicate that continuous machines theydisclose can mix satisfactorily practically everything. However, eachtype of mixer has its particular uses and limitations. The readerunfamiliar with this art in referred to the Encyclopedia of Chemicalechnology, The lnterscience Encyclopedia, Inc., New York, New York,1952, vol. 9, pp. 154-166.

Commercially, the roll mill is disappearing. lts disadvantages are wellknown. Today most rubber products reinforced with carbon black are mixedin internal mixers of the Vaned-rotor type made and sold by theFarrel-Birmingham Company, inc., Ansonia, Connecticut, under thatcompanys registered trademark, Banbury.

Prior to the present invention none of the continuous machines suggestedby prior art patents or elsewhere, have been able to supersede the openmill or the Banbury type mixer. These me the only machines that haveprovided the combination of time and temperature control and mixingintensity with each capable of variation by the operator completelyenough to permit the handling of even the toughest mixing problems.

For example, in the manufacture of rubber, mixing is the operationrequired to obtain a thorough and uniform dispersion in the rubber ofthe ingredients called for by the formula. Whether done in an open rollmill or in a Banbury type mixer, a deiinite time and temperatureschedule must be followed. If poor dispersion is encountered, the causeof trouble must be immediately established and corrected. Faultycompounding materials, too short a mixing cycle, improper temperaturecontrol, or wrong batch size may be factors to be investigated ittroubles are noted. Such investigation and adequate correction are quickand positive in the case of the batchtype machines, whereas the priorart continuous machines have not had the iiexibility required for eitherinvestigation or correction.

It has been natural that eiforts have been made to develop continuousmixing machines which could substitute adequately i'or the batch-typemachines. Most of these efforts have been directed towards the idea ofvariations of screw-type extruders and plasticators intended to becharged at one end with the unmixed material and to discharge thismaterial through the other end in a mixed condition. These machines havenot provided adequate control of time, temperature and mixing intensityto the degree demanded by work such as rubber mixing.

Any batch-type mixer introduces material handling disadvantages. Theingredients must be weighed and packed in containers which must bestored and handled for each batch. Automatic weighing and feedingmachines deliver continuously and cannot be used. Another igetentetlNov. 3, 1954 ICC disadvantage is that exactly at the end of each mixingperiod, a batch-type mixer must dump its batch. This batch usually mustgo through sheeting mills, a screw extruder or pelletizer or in someother way be passed on expeditiously for further processing. Such largeintermittent deliveries for further processing require the installationand maintenance and operation of multiple units because these arecontinuous machines which must handle large intermittently deliveredbatches.

Many years ago the Panel-Birmingham Company, inc. started a programaimed at providing a continuous mixer having the capabilities ofbatch-type mixers. Ultimately success was achieved by the presentinventors, their invention now being incorporated in a continuousmachine actually installed and operating in the research laboratory ofthe justmentioned company. Representatives of the rubber industry havehad an opportunity to see this machine doing the jobs which theypreviously thought required a mixer of the batch-type but now performedby a machine operating continuously.

Easically the present invention includes a means for forming a mixingenclosure having interspaced entrance and exit openings and containingmixing means which cannot by itself drive material through thisenclosure although it does permit material to be moved through thisenclosure while being mixed thoroughly. Therefore, the

tixing time of the material in tne enclosure is independent of theaction of the mixing means, and instead is dependent on the rate atwhich more material is pushed into the entrance opening so as to pushthrough the material already in the enclosure and cause the portionvadjacent to the exit opening to be pushed out through the latter at acorresponding rate. The mixing means may be made to introduce a lateralpush on the material to force it through the exit opening when thelatter is located laterally with respect to the enclosure. lt ispossible to control externally the rate at which the material is pushedinto the entrance opening. lt is possible to provide mixing means thatdoes not cause extensive intermingling of the material longitudinallybetween the two openings so that material just pushed in receivesextensive lateral mixing action for a time dependent on the time ittakes to travel to the exit opening which time, in turn, is dependent onthe rate at which more material is pushed into the entrance opening. Byvarying the size of the exit opening the pressure on the materialrequired to push it therethrough and therefore the pressure on thematerial being mixed, may be controlled. lt follows from the foregoing,that a continuous mixer can be made which provides for completelycontrollable mixing time and pressure which are important factorsdetermining the temperature and mixing intensity imparted to thematerial.

This new continuous machine uses the above basic principles and includesa barrel forming two laterally inter-connecting cylindrical chambershaving at one end a common lateral discharge orifice or exit opening.Contra-rotating bladed rotors work in the two chambers. The other end ofthe barrel has an entrance opening and a screw feeder provided with ahopper for receiving the material to be mixed, this screw feeder pushingor stufling the received material into the ends of the two chambers. Therate at which material is fed to this hopper may be controlled easily.

Each rotor forms oppositely projecting blades having a cross sectionalcontour which is substantially the same as that of a Banbury type mixerblade. An important difference is that each blade starts out at itsloading end with a twist that gradually turns away from or backwardlyrelative to its rotation until it arrives at a location spaced betweenthe ends of the rotor, the blade then con- Vbetween the two helicalportions of each blade is such that when the chamber contains materialthe average of any and all of any axially directed forces, that is tosay the algebraic sum ot these forces, applied to the material by therotating blades is insuicient by itself to force the material throughthe discharge orilice. The degree oi twist is such that there is noextensive circulation or pumping of the material at any localized Zonein a direction that Vis axial with respect to the rotors'and chambers.

Another distinctive feature is that the discharge orifice has ardepth inthe axial direction of the machine that is relatively Vvery small ascompared to the overall length of the chambers and rotors. The width ofthis orice in the radial or circumferential direction with respect tothe rotors, is much greater than this depth. The oriiice is like arather wide but shallow or short slot extending transversely withrespect to the machine. It is located centrally; Vacross the junction ofthe two cylinders with each other, and in overlapping relation withrespect to the adjacent endsV of the two blades or rotors. The bladesexert lateral forcesV on the material and can push material adjacent tothis oriiice out therethrougr Further, this discharge orice is providedwith walls which extend transversely outwardly from the two rotors toVform what mint be called a rectangular tube which is long enough so thatit provides a substantial frictional restraint to material dischargingthrough the orifice and theyY do have the ability to stuif the mixedmaterial through this discharge oriiice when the chambers contain enoughmaterial lengthwise. Thus the screw feeder iS v only required to movematerial to the discharge orifice.

Therefore, by controlling the rate at which the material is fed, thetravel of the material through the machine is correspondinglycontrolled.

The barrel of this new machine has hollow walls through which cooling orheating duid may be passed. High heat-exchange capacity is providedbecause the new rotorsV give great mixing action with consequentformation of'great heat, and extensive cooling may then be required. Thewalls of the orilice, referred to above, may be excessively cooled bythis cooling action and tend to cause material delivery troubles.Therefore, these walls are provided with passages for the passage ofheating duid for use when necessary to overcome such troubles.

With proper design these structural points of novelty provide for thefollowing new principles of operationt.

Assuming that the machine is in full operation, its man- Vner ofstarting being described hereinafter, the described 'rotor bladesprovide for a full Banbury type mixing a forced into the loading end ofthe machine so as to of necessity force a corresponding amounttowardsthe discharge orifice, the force feeding action of the receiving andfeeding means being adequate to put enough pressure on the materialinside of the two chambers to cause the material to move lengthwisethrough the barrels chambers to the area opposite to the dischargeorifice where the blade portions adjacent Ythereto can push lthematerial to cause the discharge by overcoming the choking restraint ofthe oriiice and its side walls.

ln effect, the two chambers and the two rotors in a lengthwise mannerform a series of the prior art Banbury type machines which. travelalong, successively being loaded and after a controlled time, unloaded.It is as tnough there were, in the new machine, a plurality oflongitudinally superimposed radially extending traveling laminations ofthe material being mixed, each blending with the other but-without themixing material in any lamination being pumped extensively into thematerial of adjacent layers. The moment enough material is charged inthe loading end to form what might be called a new lamination, the lastlamination or layer or baby Banbury type batch at the discharging end,is discharged. This action may be pulse-like or a continuous ilow. Theoperator of the machine, by controlling the rate at which the materialis charged in the hopper, can control accurately the mixin time becausehe controls the residence time of what might be called each little batchtraveling lengthwise through the machine. Pressure is controlled bycontrolling the discharge oriiice size.V

Admittedly the above is an imaginative analysis to the degree that theilow is homogeneous, but it is true in that the machine does not mixlongitudinally to any degree which might prevent all components fromremaining in the machinef o-r the same ravel time. Y n

The barrel forming the two chambers is provided with a longitudinallyextending series of individually controllable laterally extendingchambers individually adapted to conduct a ow of'heatingror coolingfluid, thus giving zone control throughout the length of the machine.Therefore, as each little so-calledbatch travels from zone to zone itsrate of cooling or heating may be controlled like the control permittedby a Banbury type machine.

Still further, by controlling the swinging wall of the discharge orificethe pressure on the material in the barrel may be controlled, whereby tocorrespond to the use of the floating Weight of a Banbury type mixer. Inthe actual operation of the machine, an automatic weighing feeder isused which, due to its construction, charges the machine intermittentlybut in rapid succession with minute charges of material. To this extentthe somewhat imaginative concept of tiny batches going through themachine is preserve-d. With completely continuous feeding, theaction'remains the same. Both give forward pressure against which theback pressure of the orice control reacts. l

When the material is rubber and carbon black, just as in the case of .abatch-type unit, there is a small chance that the carbon black maynot becompletely dispersed until at the very end of the cycle. The dischargeorice, which it will be remembered is of relatively shallow depth butrelatively great lateral extent, permits the adjacent rotor blades toshave olf or push off little increments of material at the end of thecontinuous mixing and force them through the orice so that thedischarged material representsV an average condition of the material atthe end of the machine. This has proven to be of some importance inassuring that the discharged material Vrepresents a dispersion free fromconcentrations to a degree substantially equalling that attainable by abatch-type operation. Because the components of the material beingmixed, may be fed continuously or substantially continuously, control oftheir proportioning is facilitated. With this continuous machine thecomponents may be fed by automatic machines which feed predeterminedamounts `at predetermined rates from bulk supplies, thus avoiding thematerial handling problems of batch-type machines.

As previously indicated each rotor forms two oppositely extending bladesand each of these blades extends so as to overlap the lateral ortransverse discharge orilice. The discharge orifice is located laterallybetween the travelling paths of the peripheries of the blades of the tworotors and the two rotors are powered to rotate towards this oritice.This required that the rotors contra-rotate so that as their respectiveperipheries approach each other they move towards the discharge orifice.Gne rotor may be turned faster than the other.

The lengthwise blade continuity is of importance when in conjunctionwith the contour causing each blade to first twist backwardly withrespect to its rotation and then twist forwardly with respect thereto.In addition to providing a rough bmance of the axially moving forcesapplied to the mixing material to a degree preventing the rotor actionfrom force feeding the material through the discharge orice, thelnaterin is being pushed towards the orice end ofthe barrel and at alater stage is being pushed away nom this orice end. The result is atendency to crowd the material against itself by the oppositely directedforces so that in addition to the material being smeared against theinside of its chamber while being extruded diagonally back and forthlongitudinally with respect to the rotors, it is smeared and extrudedcircumferentially with great force. A modification or variation mayconsist in providing a straight or plateau-like portion for each bladewhere the blades overlap the discharge orifice. With the blades turningtowards this orifice there is then an increased tendency to stud themixed material through the orifice which tendency becomes fully eiectivewhenever more of the material is forced or stuffed into the loading endof the barrel. Better mixing may also result.

The construction of the new continuous mixer is illustrated by theaccompanying dr wings in which:

FIG. 1 is a side elevation;

FIG. 2 is also a side elevation showing the major parts illustrated byFIG. l but with the machine opened for servicing or changing of therotors;

FIG. 3 is a top plan View of FIG. 2;

FIG. 4 is a vertical longitudinal section or" the left-hand or dischargeend of he machine, this section showing the parts of the side of thebarrel shown by FIGS. l and 2, the corresponding parts of the other halfof the barrel being substantially the same;

FIG. 5 is a section corresponding to that of EEG. 4 but showing theright-hand or charging end;

FIG. 6 is a cross section taken on the line 6 6 in FIG. 4;

IG. 7 is a perspective view showing details of the discharge orificeassembly;

FIG. 8 is a cross section talren on the line @-3 in FIG. 4;

FIG. 9 is a perspective view showing a loclf. which normally holdstogether the parts shown opened in FIGS. 2 and 3;

FIG. l() is a side view showing one of the rotors;

FIG. 11 is a side view showing the other or" the two rotors;

FIG. 12 is a cross section taken on the line ft2-l2 in FIG. 11;

FIG. 13 is a detail View in cross section showing the water heating orcooling action that occurs internally within the rotors;

FIG. 14 is a view similar to FIG. 10 but showing a modification of theblade contour;

FIG. 15 is a cross section taken on the line it-l5 in FIG. 14; and

FIG. i6 is a cross section taken on the line l-lo in FIG. 14.

As shown by FIG. 1, the main exposed parts of this new mixer comprisethe barrel l with its associated parts, the discharge orifice assembly2, and the feeder 3 which receives the material to be mixed and stur'fsit under pressure into the loading end of the barrel. In addition, thereis a pinion housing 4 containing the intermeshed pinion gears forcausing contra-rotation of the rotors, and a gear box 5 containing speedreduction gearing. A powered rotary shaft 6 is connected by a coupling 7with the input shaft il of the gear box 5, the latters output shaft 9being connected by a coupling l@ with the input shaft il for the piniongears within the housing 4.

@poration of the machine consumes considerable horse power at hightorque and so the pinion housing iand gear box 5 must be large andheavy. Both of them are mounted stationary on a firm base constructionl2.

The barrel l and its associated parts and the feeder 3 are mounted toslide horizontally to and from the above stationary parts. At the lefthand or discharge end the barrel I has depending supports l and at thefeeding or loading or right hand end the barrel l has depending supports14. These supports ride in guideways IS which are a part of the baseconstruction 12. A horizontal transverse shaft 16 carries a pinion geari7 which meshes with a horizontal longitudinally extending rack gear 1Sthat is xed to the stationary base construction l2.

The barrel l and feeder 3 are rigidly interconnected to form a unit anda quick-releasable lock l@ normally locks the feeder 3 rigidly to thepinion housing 11. When the lock 19 is released the pinion gear 17 maybe turned by a crank 26 to slide the unit comprising the parts l, 2 and3, away from the pinion housing d. This exposes the rotors as shown byFIGS. 2 and 3. As previously indicated, the design of these rotors isimportant.

As shown by FIG. 12 the cross sectional design of these rotorscorresponds generally to the cross sectional design of the oldbatch-type Banbury-type rotor blades. The diiference is that as shown byFIGS. 10 and 11, as well as by FlGS. 2 and 3, the oppositely projectingblades start out at their loading or right hand end with a twist orhelical section 2l that generally turns away from or backwardly relativeto the rotor rotation, until they arrive at a location spaced betweenthe ends of the rotor. Then the blades continuously and withoutinterruption twist in the opposite direction, as at 22, towards thedischarging or left hand end of the rotor. The junctions between theoppositely twisting or helically contra-pitched portions of each bladeare in the form of apices 23 in the case of the forms shown by FIGS. 13and 14.

Because the rotors contra-rotate the twist of the helical portions ofthe oppositely extended blades of each is opposite to the pitch of theother. This can be seen by examining FIGS. 3, 1G and 11, the latter twogures showing in enlarged scale the pair of rotors shown installed inthe machine.

The rotor of FIG. l1 is the one towards the observer in FlG. 2 and itintegrally includes the shaft 11 that can be seen in FIG. 1 connectingwith the coupling lil. This shaft mounts this rotor by being journaledin spherical anti-friction bearings 24 mounted by the pinion housing 4.Rotor thrust is almost absent and these bearings are adequate. One or"the pinion gears 25 is keyed to this shaft and the other pinion gear 2o,required for contrarotation, is keyed to a shaft Ila of the rotor shownby FIG. 10 and which is correspondingly mounted by unillustratedanti-friction bearings located behind the plane of FIG. 5, by the pinionhousing 4. These bearings are similar to the bearings 24 that can beseen in FIG. 5.

As shown by FIG. 2 the rotors project as cantilevers from the pinionhousing 4 when the movable parts are slid away or opened from thestationary parts. Thus servicing and cleaning are made easy, and whendesired the rotors may be easily removed and replaced by others. Bothrotors by normal engineering methods may be mounted so that they may bequickly pulled from the pinion housing 4 when desired.

The rotors each have a bore 27 extending throughout their bladedportions and opening from their ends opposite to their shafts 11 andlla. These ends each form a stub shaft 28 that is externally smooth.These stub shafts are slidingly received within tubular journals 29running in plain bearings 29a mounted by a bracket 3@ secured to theleft hand end of the barrel 1. Pins 3l key the shafts 23 to the journals29. The open ends of the bores 27 are provided with counter bores 27awhich slide over the connectors 32 of commercially available fluid inletand outlet couplings 33 secured to the bracket 30, one for each of therotors. The connectors 32 have O rings 34 for sealing with the counterbores 31 and provide projecting pipes 33 which extend into the bores 27almost to their inner or right hand ends. The units 33 each has an inlet35 and an outlet 36, the inlet 35 connecting with the pipe 33 and theoutlet 36 connecting with the space between the pipe 33 and the insideof the bore 27, in each instance. The rotors are free to rotate relativeto these couplings 33.

When the partsrare slid apart or separated to expose the two rotors, therotor shaft 2S can freely separate from the journals 29 and theconnectors 32 described above. The sliding surfaces of the journals 29and plain bearings 2da are ordinarily kept free from dirt and theirlubrication is retained by seals 37. Seals 33 engage the lett hand buttends of the rotors during operation of the mixer to prevent any loss ofthe material being mixed when the mixer is in operation, and these sealsalso permit Vthe described separation of the parts.

Between the right hand shaft portions l1 and lla and the blades, eachrotor has a helical feed screw 39 of the properpitch for its rotation tofeed material towards its blade. These fit in cylinders il formed asforward'extensions oi the two cylindrical chambers of the barrel 1described in detail heretofore. Vertical ports 41 fed by a common hopper42 serve to feed the material to be mixed to the feed screws 39 whichthen stuif the material to the left and into the loading ends of thechambers of the barrel l, Seals 43 prevent loss of material to theright, keeping in mind that the feeding action is in the oppositedirection. All of these parts permit the longitudinal sliding requiredto open up the mixer for exposure of the rotors.

The barrel 1 internally forms the two parallel laterally interconnectingcylindrical chambers 44 in which the rotors rotate. VThe relativediameters of the rotors and of these chambers le are such as to leave aspace between the rotor tips and the chamber walls through Vwhich thematerial may be extruded while being smeared against the chamber walls.rThe barrel is hollow for receiving cooling or heating fluid and isdivided lengthwise into a plurality of sections each separate from theother and each having its own iiuid inlet 45 and outlet 46. Thus foreach section a cooling space 47 is provided which is isolated from thecooling spaces of the other sections so as to lengthwise of the barrelprovide for zone temperature control throughout the length ofthe barrel.In each instance the cooling space 47 is large and the inner wall oftheV barrel forming the chamber 44 isY externally finned as at 43 toprovide great heat exchanging capacity. The dividing wall 49 between thechambers and each cooling section has a vertical bore Sti which extendsinto the interior rotor chamber space at a location intersecting Vthelateral intercommunicating spaces between the two chambers. The purposeof these bores 50 is described later.

The common discharge oriiice for the two cylindrical chambers 44 isshown in FIGS. 4, 6 and 7 in detail. There it can be seen that thebarrel 1 is formed at its discharge end to provide a rectangulardepending opening l in which a discharge orifice assembly 52 is slidablyfitted. This assembly is locked in position by a releasable screw 53which can be backed ci to permit the assembly to be removed downwardlyfrom the barrel so that the assembly may be cleaned or otherwiseserviced. As shown by FIG. 4 a part of the bracket 34B coninesgthe lefthand side of the assembly 52 and in an emergency this bracket may beremoved so as to more fully release the assembly 52. rflac bracket 30 isscrew fastened to the barrel l and is therefore removable.

ln more detail, the assembly 52! has a front wall 54 that extendsupwardly to a point 55 while tapering in thick- Y nes to this point. Thepoint 55 is located directly behind the short upstandinu iat topped wall56 where the lower mutually adjacent portions of the two chambers 44join together, the space above the top of the wall 56 providing thelateral intercommunication between the Ytwo chambers d4. The describedconstruction of the wall 54 provides for a streamlined effect withrespect to the flow of the mixed material when it is forced from thebarrel. The assembly 52 includes the sidewalls 57 and the back wall 5Swhich is hinged at its top edge so that it may be swung inwardly towardthe wall 54 more or less, under the control of a screw 59 having a ilatsided end 60 to which a wrench may be applied. This screw 59 is inthreaded arrangement with a nut 6l pivotally connected to an arm/62extending from the supports i3, and the screw 59 connects with the wall5S by a pivotal connection 63. All of the walls of the assembly 52 areprovided with iiuid passages 64 provided with suitable connections 65 sothat fluid may be passed through the walls to provide for temperaturecontrol of the orifice assembly.

lt is tc be noted that as shown by FIG. 6 the width of the orificeprovided by the assembly 52 is relatively great, it encompassing almostthe whole of the two mutually adjacent lower circumferential quarters ofthe two chambers dfi. 0n the other hand as can be seen from FIG. 4 thedepth or extent in an axial direction with respect to the rotors is veryshort as compared to the overall length of the rotors. Furthermore, thevertical length of the walls of the assembly 52 is of relatively greatextent. This length exceeds the radius of the chambers 44 as theconstruction is illustrated.

Rigidity between the barrel l and feeder 3 with respect to the pinionhousing 4 depends on the quick releasable lock 19. As shown by PIG. 9the right hand end of the feeder 3 is provided with a pair of verticallyinterspaced, mutually parallel castellated bars 66. The left hand end ofthe pinion housing 4 is provided with two mutually superimposed pairs ofcorresponding bars 67 and 63, located so that the bars 66 may passcompletely across them in intermeshing relationship and so that the bars66 are then located in spaces 69 between the bars 68 and the left endface of the pinion housing fl. The bars 68 may be longitudinally shiftedby means of screws 70 and when the bars 66 are located in the spaces 69these screws 76 are used to shift the bars 65 so as to lock the bars 66against retreating from the pinion housing. In this fashion a firminterlocking is effected which is at the same time easily releasable.

The vertical bores dll which extend into the chambers of the barrel Ilat various locations, are used for various purposes, or they may beplugged closed in one or more instances. The general purpose of thesebores is to permit the mounting of thermo-couple elements or the like inthe temperature-controlled zones of the machine, In some instances itmay be desired to introduce uids to the material being mixed atpredetermined phases of the mixing action, the addition of oil being anexample, and in such instances pipes may be connected to one or anotherof the bores 50 registering with the mixing zone or zones where theaddition is desired.

As shown by FIG. l these bores 50 have thermo-couple units 7l screwedinto each of them and these units are connected to a tetmperatureindicating device 72 having a scale 75. This instrument is provided witha selector switch 74 so that any one of the four thermo-couples may beconnected with the instrument 72 so that the scale 73 indicates thetemperature of the material being mixed in the zone where the selectedthermo-couple is located.

The manner of making the illustrated machine should be understandabletoanyone skilled in the design and construction of heavy duty mixers ofthe Banbury-type. rl`he barrel can be made by metal casting techniques,this also applying to the pinion housing and obviously to certain otherparts. The rotors may be machined from solid metal using the machineshop practices which are also used to make Banbury-type mixer rotors.The drawings show various details that have not been referred tospecifically because their function and nature should be apparent. Forexample, the plain bearing 29 is held in position in the bracket 39 by aset screw 29a and the bearing is adapted to be flooded with lubricantapplied through a screw blocked passage 37a, seals 37 preventing loss ofthis lubricant. As previously indicated tbe part 33 is a commerciallyobtainable item. The shaft holes for the pinion housing 4 are providedwith seals 24a for retaining the lubricant with which this housing wouldordinarily be filled. Ordinarily the rotors would not be pulled from thepinion stand very often and when this is done the pinion housing 4 maybe emptied of its lubricant. In FIG. 1 the pinion housing t is shown asprovided with a lubricant level gauge 24h and an inlet 24C through whichthe lubricant is poured into the housing originally. In general theindividual parts are held together by screws which have not beendescribed specifically.

It was previously mentioned that this new continuous machine may be fedcontinuously or substantially continuously with the material to be mixedand therefore, in FIG. l automatic weighing feeders 76 and 77 are shownfeeding into the hopper 42 of the feeder 3. These machines 76 and 77 arecommercially available and operate to deliver intermittenly but in veryclose succession, accurately weighed quantities of material. Theintermittent feedings are so close together as to be in effectcontinuous and, if desired, automatically feeding-rate controlledmachines can be designed for truly continuous flow delivery.

Operation In the case of the batch-type mixer of the Banbury-type it isnecessary to determine and establish the mixing schedule by running atest program aimed at setting up the mixing time, temperature control,horse power and the other variables which are available and whichprovide for the nice degree of mixing control for which these mixers arefamous.

Correspondingly, with the new machine and its corresponding ilexibilityof the various mixing control factors, corresponding accurateestablishment of mixing schedules is possible.

With the above in mind, the machine with its parts locked together asshown by FIG. 1, and with its rotors rotating by a suitable power sourcedriving through the coupling 7, the two chambers 44 are first loadedwith the material to be mixed.

This is done by loading the material through the hopper 42, the screwblades 39 forcing the material forwardly into the chambers and theswinging wall 58 being adjusted to a ow choking position. With thechambers loaded the screw blades 39 continually try to press thematerial towards the left while the orifice assembly 52 prevents thematerial from leaving the chambers. Consequently, the material in thechambers is placed under pressure and experiences the typicalBanbury-type action excepting that the familiar longitudinal pumping orilowing is substantially absent. At this time the scale 73 of thetemperature measuring instrument 72 of course shows a rapid temperaturerise throughout the various zones of the barrel 1, and cooling waterflowed through the various chambers 47 is used to restrict thetemperature rise. Cooling water flowed through the bores 27 of therotors keeps the latter from becoming excessively hot.

Now by controlling one or the other or' both of the automatic feeders 76and 77, the substantially continuous feed of `the material into thehopper 42 of the feeder 3 is adjusted. At this time the swinging wall 53is gradually swung outwardly to reduce the discharge choking eifect ofthe orifice assembly 52. Continuous or substantially l@ continuous ilowconditions are now beginning to be established.

Control of pressure within the mixer under these continuous liowconditions is under full control by varying the discharge choking actionof the orifice assembly 52. As the blades counter rotate towards themouth of this assembly they continuously try to stuff material throughthe orifice provided by the four rectangular walls of this assembly.Discharge is resisted both by the choking effect alforded by adjustmentof the swinging wall 58 and by the length of the orifice. Temperaturecontrol of the orifice assembly is available by introducing waterthrough the various passages 64 and as previously indicated this mayrequire the use of hot iluid so that the discharging material is notexcessively cooled. t can be seen that pressure control within the mixeris variable to correspond to the control provided by adjusting thepressure on the floating weight of a Banbury-type mixer.

Total mixing time is under complete control because this depends uponthe rate at which the automatic feeders 76 and 77 are adjusted -to feedthe material. This cannot provide mixing time control satisfactorilywhen using screw type continuous mixers.

Mixing time control is where the peculiar contour of the new rotors isof such great importance. As each little increment of material fed tothe hopper 42 is stuffed by the screw blades 39 into the right hand endof the barrel l, it receives a forward or left hand moving force fromthe helical or twisted portions 2l of the rotor blades. However, thematerial cannot go forwardly because of the counter pressure exerted onpreviously fed material by the portions 22 of the blades which areattempting to move the material backwardly. The two helical portions ofeach blade apply oppositely directed forces to the material which canmove forwardly only to the degree that the increased pressure on thematerial in the chambers, due to the constant feeding of unmixedmaterial, is sufficient to provide excess material which the rotorsdrive through the discharge orifice against the counter pressure orchoking exerted by the latter. The resistance is due to the frictionwith the long orifice passage and the natural choking due to thedimensions and shape ofthe orifice cross section.

The newly added material at the right hmd end of the chambers begins tomix. Any pumping action longitudinally with respect to the chambers islimited to a circumferentially sinuous motion as the material is smearedagainst the walls of the chambers, starts to move a little forwardlywhen close to the advancing rotor blades and is then extruded backwardlyreversely between the rotor blades and the chamber walls through thespace between these two. It can be seen that there is a typicalBanburytype mixing action but that for the tiny batch of material justadded it is strictly localized lengthwise of the chambers.

With the addition of more material the above little batch, as it were,is shifted by the volume of the added material towards the left ordischarge end of the mixing chambers. Mixing continues all the time butthe partially mixed material cannot get to the discharge end of thechambers so as to discharge prematurely in only a partially mixedcondition.

Keep in mind that in referring to small batches this is done merely forconvenience of explanation. The analogy is accurate however, because asmaterial is introduced to the loading end of the chambers it travelslengthwise through the latter without being pumped back and forth so asto result in its premature discharge through the discharge orifice.

As the material travels lengthwise while under the constant Banbury-typemixing action its temperature naturally rises just as it would in abatch type machine of the Banbury-type. This temperature rise is keptfrom becoming excessive by controlling the Water flow through thevarious barrel chambers 47 each of which is separate mixing schedule ofthe batch type mixer.

from the other and provided with its own water inlet'and` outlet. Bythrowing the selector switch 74 from Vone to another of thethermo-couple units 71 conditions can be ascertainedY at the variouslocations in the chambers.

Ordinarily the temperature of the material should be adjusted to preventharm to the material being mixed. Thismay require extensive watercooling and `as previously indicatedV this may require such extensivecooling at the discharge end of the barrel as to necessitate the use ofhot fluid for replacing the heat lost by the discharge orifice assembly52. ln other words the use of hot water through the passages 64 providesa heatrshield between the discharging material and the heavily cooledbarrel.

Maximum production rates demand the shortest possible mixing timecompatible with complete mixing. Assuming that one of the feeders 76-77is feeding rubber and the other is feeding carbon black or some otherma-V terial that introduces severe mixing problems, complete mixing ispossibly just being effected almost at the very discharge endV of thechambers. Since the rotors stuff the material slowly through thedischarge orifice assembly 52 it might happen that this is done prior tocomplete mixing when maximum production rates are attempted. However,the very short depth or extent of the discharge orifice `in the axialdirection of the chambers and rotors, reduces this possibility to aminimum. The transverse Width provides a passage of adequate overallcross sectional area. Therefore, no trouble is experienced under normalconditions with the presence of unmixed particles or lumps or carbonblack or other material.

Just as when operating a Banbury-type mixer of the batch type, it isrealistic to realize thatwhen operating the new continuous mixerproblems may arise. These are immediately detectable because of thecontinuous discharge oi material and they are immediately correctablebecause mixing time, mixing pressure, mixing temperature, and mixingintensity through horse power control, are all under immediate and fullcontrol.

Obviously control applies to the composition of the material fed becausethe feeding rate of commercialV weighing and feeding machines are easilyvariable. Although only two of these weighing and feeding machines areshown it is contemplated that a large number may be used depending onthe mixing formula required. The flexibility of control of the newmachine, instead of being a rigid and xed matteras in the case of priorart continuous mixers, is under full control to an extent that evenexceeds that possible when using the reliable Banbury-type batch mixer.

Once a mixing schedule is set it is unnecessary to use the multiplicityof temperature measuring devices located throughout the length of thebarrel. Then some or all of the bores i? may be used for theintroduction of mixing components. In this way components can be addedwhich would normally be added part way through the Oil is an example ofthe type of material that may be added at a later time.

A machine constructed as illustrated and described hereinabove has run along test program and been used for many demonstrations to skeptics whodid not believe a continuous machine could do the job of the prior artBanbury-type batch type machine- A modification of the rotor design isshown by FiGS. 14`l6 wherein the sections corresponding to generallysimilar sections shown by FIGS. -12 are correspondingly numbered usingthe letter a for identification while, in addition, providing straightportions 23a. In this case each Yof the portions described has a lengthapproximating one-third the overall length of the rotor blade.

What is claimed is: Y

l. A continuous internal mixer comprising a barrel forming two laterallyinterconnecting substantially cylindrical and mutually parallel chambershaving at one end g rotating said rotors, each of said rotors having ablade with a cross section that is substantially like that ofV aBanbury-type blade and having a portion that twists away fromitsdirection of rotation and a portion that twists in the oppositedirection, the length and twist ratio between said oppositely twistingportions of said blade being such that when saidV chambersV contain saidmaterial' the average of the axially directed forces applied to thelatter by said blades is insufiicient to force the material through saidorifice, whereby the overall axial travel of said material through saidchambers is dependent on the rate at which it is received by thefirstnamed means.

2. A continuous internal. mixer comprising a barrel forming twolaterally interconnecting substantially cylindrical andV mutuallyparallel chambers having at one end al common discharge orifice, bladedrotors located in said chambers,A means for receivingk the material tobermixed and stuiiing it Vunder pressure into said chambers at alocation spaced from said discharge orifice, means for rotating saidrotors, each of said rotors having a blade Y, with a cross section thatis substantially like that of al Banbury-type blade and having aportionthat twists away from its direction of rotation and a portionV thattwists in the opposite direction, the length and twist ratio betweensaid oppositely twisting portions of said blade being such that whensaid chambers contain said material the average of the'axially directedforces applied to the latter by said blades is insufiicient to forcevthe material through said oriiice, whereby the overall axial travel ofsaid material through said chambers is dependent on the rate at which itis received by the first named means; said discharge orifice openingtransversely from said chambers and at least mainly in overlappedrelation with respect to the portions of said blades adjacent thereto.

3. A continuous internal mixer comprisingV a barrel forming twolaterally interconnecting substantially cylindrical and mutuallyparallel chambers having at one end a common discharge orice, bladedrotors located in said chambers, means for receiving the materialv to bemixed and stufiring it under pressure into said chambers at a locationspaced from said discharge orifice, means for rotating said rotors, eachof said rotors having a blade with a cross section that is substantiallylike that of aV Banbury-type blade and having a portion that twists awayfrom its direction of rotation and a portion that twists in the oppositedirection, the length and twist ratio between said oppositely twistingportions of said blade being such that when said chambers contain saidmaterial the average of the axially directed forces applied to thelatter by said blades is insufficient to force the material through saidorifice, whereby the overall axial travel of said mate-- rial throughsaid chambers is dependent on the rate at which it is received by thefirst named means; said discharge orifice opening transversely from saidchambers and having a depth in the axial direction of said chambers thatis relatively small as compared to the overall length of said chambersand rotors, and having a width that is substantially greater than itsdepth, said orifice being located centrally across the junctions of saidchambers and at least mainly in overlapped relation with respect to theportions of said blades adjacent thereto.

4. A continuous internal mixer comprising a barrel forming two laterallyinterconnecting substantially cylindrical and mutually parallel chambershaving at one end a common discharge oriiice, bladed rotors located insaidv chambers, means for receiving the material to be mixed andstuffing it under pressure into said chambers at a location spaced fromsaid discharge orifice, means for rotating said rotors, each of saidrotors having a blade with a cross section that is substantially likethat of a Banbury-type blade and having4 a portion that twistsaway fromits direction of rotation and a portion that twists in the oppositedirection, the length and twist ratio between said oppositely twistingportions of said blade being such that when said chambers contain saidmaterial the average of the axially directed forces applied to thelatter by said blades is insutiicient to force the material through saidorifice, whereby the overall axial travel of saidmaterial through saidchambers is dependent on the rate at which it is received by the firstnamed means; said discharge orifice opening transversely from saidchambers and having a depth in the axial direction of said chambers thatis relatively small as compared to the overall length of said chambersand rotors, and having a width that is substantially greater than itsdepth, said orifice being located centrally across the junctions of saidchambers and at least mainly in overlapped relation with respect to theportions of said blades adjacent thereto; said orifice being providedwith walls which extend transversely from said rotors to form what issubstantially a rectangular tube long enough to cause substantiallyincreased restraint to said material when discharging therethrough.

5. A continuous internal mixer comprising a barrel forming two laterallyinterconnecting substantially cylindrical and mutually parallel chambershaving at one end a common discharge oriiice, bladed rotors located insaid chambers, means for receiving the material to be mixed and stuingit under pressure into said chambers at a location spaced from saiddischarge orifice, means for rotating said rotors, each of said rotorshaving a blade with a cross section that is substantially like that of aBanbury-type blade and having a portion that twists away from itsdirection of rotation and a portion that twists in the oppositedirection, the length and twist ratio between said oppositely twistingportions of said blade being such that when said chambers contain saidmaterial the average of the axially directed forces applied to thelatter by Said blades is insufficient to force the material through saidorifice, whereby the overall axial travel of said material through saidchambers is dependent on the rate at which it is received by the iirstnamed means; said discharge orifice opening transversely from saidchambers and having a depth in the axial direction of said chambers thatis relatively small as compared to the overall length of said chambersand rotors, and having a width that is substantially greater than itsdepth, said orice being located centrally across the junctions of saidchambers and at least mainly in overlapped relation with respect to theportions of said blades adjacent thereto, said orice being provided withwalls which extend transversely from said rotors to form what issubstantially a rectangular tube long enough to cause substantiallyincreased restraint to said material when discharging therethrough; andmeans for varying the interspacing of two of said walls to Vary saidrestraint.

6. A continuous internal mixer comprising a barrel forming two laterallyinterconnecting substantially cylindrical and mutually parallel chambershaving at one end a common discharge oriiice, bladed rotors located insaid chambers, means for receiving the material to be mixed and stutlingit under pressure into said chambers at a location spaced from saiddischarge orifice, means for rotating said rotors, each of said rotorshaving a blade with a cross section that is substantially like that of aBanbury-type blade and having a portion that twists away from itsdirection of rotation and a portion that twists in the oppositedirection, the length and twist ratio between said oppositely twistingportions of said blade being such that when said chambers contain saidmaterial the average of the axially directed forces applied to thelatter by said blades is insuiicient to force the material through saidoriiice, whereby the overall axial travel of said material through saidchambers is dependent on the rate at which it is received by the iirstnamed means; said discharge orifice opening transversely from saidchambers and having a depth in the amal direction of 1d said chambersthat is relatively small as compared to the overall length of saidchambers and rotors, and having a width that is substantially greaterthan its depth, said orifice being located centrally across thejunctions of said chambers and at least mainly in overlapped relationwith respect to the portions of said blades adjacent thereto, saidorifice being provided with walls which extend transversely from saidrotors to form what is substantially a rectangular tube long enough tocause substantially increased restraint to said material whendischarging therethrough, means for varying the interspacing of two ofsaid walls to vary said restraint; and heat exchanging means for saidwalls.

7. A continuous internal mixer comprising a barrel forming two laterallyinterconnecting substantially cylindrical and mutually parallel chambershaving at one end a common discharge oriiice, bladed rotors located insaid chambers, means for receiving the material to be mixed and stuhngit under pressure into said chambers at a location spaced from saiddischarge orice, means for rotating said rotors, each of said rotorshaving a blade with a cross section that is substantially like that of aBanbury-type blade and having a portion that twists away from itsdirection of rotation and a portion that twists in the oppositedirection, the length and twist ratio between said oppositely twistingportions of said blade being such that when said chambers contain saidmaterial the average of the axially directed forces applied to thelatter by said blades is insuicient to force the material through saidorifice, whereby the overall axial travel of said material through saidchambers is dependent on the rate at which it is received by the firstnamed means, said discharge orifice opening transversely from saidchambers and at least mainly in overlapped relation with respect to theportions of said blades adjacent thereto and having means for forming apassage extending therefrom and which is long enough to causesubstantially increased restraint to said material when dischargingtherethrough; and means for varying the temperature of said passage.

8. A continuous internal mixer comprising a barrel forming two laterallyinterconnecting substantially cylindrical and mutually parallel chambershaving at one end a common discharge orifice, bladed rotors located insaid chambers, means for receiving the material to be mixed and stuingit under pressure into said chambers at a location spaced from saiddischarge orifice, means for rotating said rotors, each of said rotorshaving a blade with a cross section that is substantially like that of aBanbury-type blade and having a portion that twists away from itsdirection of rotation and a portion that twists in the oppositedirection, the length and twist ratio between said oppositely twistingportions of said blade being such that when said chambers contain saidmaterial the average of the axially directed forces applied to thelatter by said blades is insu'icient to force the material through saidoriiice, whereby the overall axial travel of said material through saidchambers is dependent on the rate at which it is received by the iirstnamed means; said blades each extending continuously withoutinterruption for its entire length and forming a portion between itsoppositely twisting portions which is free from twist.

9. A continuous internal mixer comprising a barrel forming two laterallyinterconnecting substantially cylindrical and mutually parallel chambershaving at one end 'a common discharge oriiice, bladed rotors located insaid chambers, means for receiving the material to be mixed and stufngit under pressure into said chambers at a location spaced from saiddischarge orifice, means for rotating said rotors, each of said rotorshaving a blade with a cross section that is substantially lilre that ofa Banbury-type blade and having a portion that twists away from itsdirection of rotation and a portion that twists in the oppositedirection, the length and twist ratio between said oppositely twistingportions of said blade being such that when said chambers contain saidmaterial the aver- 3,1 sesos ing means for mounting the other ends ofsaid rotors with the Vlatter projecting therefrom as cantilevers, saidybarrel havinu mountinr means ermittin it to be moved axially from saidrotors to expose the latter for servicing.

10. A continuousinternal mixer comprising a barrel forming two laterallyinterconnecting substantially cylindrical and mutually parallelchambers'having at one end a common discharge orifice, bladed rotorslocated in said chambers, means for receiving the material to be mixedand stuiing'in under pressure into said chambers at a location spacedfrom said discharge orice, means for rotating said rotors, each of saidrotors having a blade with a cross section that is substantially likethat of a Banbury-type blade and having a portion that twists away fromits direction of rotation and a portion that twists in the oppositedirection, the length and twist ratio between said oppositely twistingportions of said blade being such that when said chambers contain saidmaterial the average of the axially Vdirected forces applied to thelatter by said blades is insutlicient to force the material through saidorifice, whereby the overall axial travel of said material through saidchambers is dependent on the Vrate at which it is received by the firstnamed means, said barrel mounting slidinoly releasable bearings for therotors ends adjacent to saidV orice, said rotor rotating means includingmeans for mounting the Vother, ends of said rotors with the latterprojecting therefrom as cantilevers, said barrel having mounting meanspermitting it to be moved axially from said rotors to expose the latterfor servicing; said rotors being hollow and having quick detachableiiuid connections adjacent to saidrbearings which separate when saidbarrel is moved axially to expose said rotors. A

11` A'continuous internal mixer comprising a barrel forming tvolaterally interconnectirur substantially cylindrical and mutuallyparallel chambers having at one end a common discharge Yoriice, bladedrotors located in said chambers, means for receiving the material to bemixed and stufiinfy it under pressure into said, chambers at a locationspaced from said discharge orifice, means for rotating said rotors, eachof said rotors having a blade with a cross section that is substantiailyiike that of a Banbury-type blade and having a portion that twists' awayfrom its direction of rotation and a portion that twists in the oppositedirection, the length and twist ratio between said oppositely twistingportions of said blade being such that when said chambers contain saidmaterial the averageV of the axially directed forces applied to thelatter by said blades is insuflicient to force the material through saidoritice, whereby the overall axial travel of said material through saidchambers is dependent on the rate at which it is received by the iirstnamed meansfsaidtdischarge orifice opening transversely from saidchambers and at least mainly in overlapped relation with respect to theportions of said blades adjacent thereto; said blades each extendingcontinuously without interruption for its` entire length and forming astraight portion extending substantially parallel to the rotors axis andlocated at its end which is overlapped by said discharge oriiice.

References Cited in the file of this patent UNETED STATES PATENTS

1. A CONTINUOUS INTERNAL MIXER COMPRISING A BARREL FORMING TWO LATERALLYINTERCONNECTING SUBSTANTIALLY CYLINDRICAL AND MUTUALLY PARALLEL CHAMBERSHAVING AT ONE END A COMMON DISCHARGE ORIFICE, BLADED ROTORS LOCATED INSAID CHAMBERS, MEANS FOR RECEIVING THE MATERIAL TO BE MIXED AND STUFFINGIT UNDER PRESSURE INTO SAID CHAMBERS AT A LOCATION SPACED FROM SAIDDISCHARGE ORIFICE, MEANS FOR ROTATING SAID ROTORS, EACH OF SAID ROTORSHAVING A BLADE WITH A CROSS SECTION THAT IS SUBSTANTIALLY LIKE THAT OF ABANBURY-TYPE BLADE AND HAVING A PORTION THAT TWISTS AWAY FROM ITSDIRECTION OF ROTATION AND A PORTION THAT TWISTS IN THE OPPOSITEDIRECTION, THE LENGTH AND TWIST RATIO BETWEEN SAID OPPOSITELY TWISTINGPORTIONS OF SAID BLADE BEING SUCH THAT WHEN SAID CHAMBERS CONTAIN SAIDMATERIAL THE AVERAGE OF THE AXIALLY DIRECTED FORCES APPLIED TO THELATTER BY SAID BLADES IS INSUFFICIENT TO FORCE THE MATERIAL THROUGH SAIDORIFICE, WHEREBY THE OVERALL AXIAL TRAVEL OF SAID MATERIAL THROUGH SAIDCHAMBERS IS DEPENDENT ON THE RATE AT WHICH IT IS RECEIVED BY THE FIRSTNAMED MEANS.